For mounting a semiconductor component, such as a chip comprising integrated circuitry, on an external substrate, such as a circuit board, it is a well-know technique to bond the semiconductor component to the external substrate by means of projecting electrodes on an internal substrate of the semiconductor component. The projecting electrodes often take the form of bumps. Note that the internal substrate of the semiconductor component will hereinafter be referred to in short as “substrate” while the external substrate will always be referred to as the “external substrate” without abbreviation.
Mechanical stress between the projecting electrode and the substrate or, in a component-external-substrate assembly, also between the projecting electrode and the external substrate can be caused by differences between the coefficients of thermal expansion of the component and of the external substrate. For the component is typically based on silicon and further comprises layers of metal and layers made of insulators, while the external substrate is often made of an organic material, exhibiting a different behavior during temperature changes. Such mechanical stress due to a difference in thermal expansion coefficients can produce a crack of an isolation layer on the substrate of the semiconductor component, a delamination of layers, or even a breakout of silicon. On the side of the external substrate, a delamination of films arranged on the circuit board has been observed due to exerted mechanical stress.
U.S. Pat. No. 6,995,474 B1 describes an assembly of a semiconductor component with an external substrate that comprises a semiconductor component in the form of a liquid crystal display device. As shown in FIG. 6 of U.S. Pat. No. 6,995,474 B1, the device has an integrated circuit on a substrate and a projecting electrode that mechanically and electrically connects the substrate to an external glass substrate to form a chip-on-glass (COG) assembly. In order to provide the projecting electrode as a flexible bump for stress compensation, a projecting electrode has conductive pellets contacting the external glass substrate and covered by a conductive connection part in the form of a plate. The conductive connection part is connected with the substrate that contains the integrated circuit by a structure that comprises conductive parts in the form of posts embedded into an insulation layer, which is for instance a polyimide. A projecting electrode can contain a one-dimensional or two-dimensional array of posts embedded in the insulation layer, as disclosed by FIGS. 9-17 of U.S. Pat. No. 6,995,474 B1. A stress compensation is enabled by a combination of the flexible insulating material between the posts, such as polyimide, and the pellets, which allow some sliding motion of the connection part on top to compensate mechanical stress.
The structure of the projecting electrode disclosed in U.S. Pat. No. 6,995,474 B1 is rather complex. This increases the process complexity during fabrication of the projecting electrode and therefore the cost of the semiconductor component as well as the cost of the component-external-substrate assembly.